Silicon carbide furnaces and plants



March 11, 1969, 'w. T. BOLKCOM ETAL. 3,43 ,605

SILICON CARBIDE FURNACES AND PLANTS I Filed Feb. 25, 1967 Sheet of 4 I INVENTORS March 11, 1969 w. 1-. BOLKCOM ETAL SILICON CARBIDE FURNACES AND PLANTS 7 Filed Feb. 23, 1967 Shet i of 4 w. T. BOLKCOM ETAL 3,432,605 SILICON CARBIDE FURNACES AND PLANTS March 11, 1969 Sheet Filed Feb. 23, 1967 March 11, 1969 w. 'r. BO LKCOM E TAL I SILICON CARBIDE FURNACES AND PLANTS Sheet Filed Feb. 23, 1967 Mam T1508 /T/ AW M a W n u m m lllllllllllllllllll Il w w u 1 u L n L 7. I t: 1 T 11 ,1vlm .1 Wm J I; J Ti on 51! n rllilll11:1 :12 Fl... llllllllllllllllllll i1.

3,432,605 SILICON CARBIDE FURNACES AND PLANT Wilbur T. Bolkcom, Pittsburgh, and William E. Knapp,

Allison Park, Pa. (both American Metallurgical llggggcts Co., 9800 lvI'cKnight Road, Pittsburgh, Pa.

Filed Feb. 23, 1967, Ser. No. 618,034 [1.5. Cl. l3-20 a 10 Claims Int. Cl. Hb 3/02, 3/62 ABSTRACT OF THE DISCLOSURE A silicon carbide manufacturing plant for manufacturing silicon carbide in a movable fumace'at one area, discharging the furnace in a second area and loading in a third area. An electrical power source is provided having a main trackway adjacent the power source with a furnace car movable to and from said power source and removably connected thereto through electrodes .on end panels on the car.

This invention relates to silicon carbide furnaces and plants and particularly to a silicon carbide furnace which can be fired in one position, removed to a second position for cooling and unloading and to a plant incorporating a plurality of such furnaces.

In the past silicon carbide has been manufactured in stationary electric furnaces. Such stationary furnace installations usually require four to six furnaces for each transformer in order to utilize the transformer to its maximum efficiency, with one furnace heating, one being unloaded, one loading, and the remainder cooling. This rcquiresvery large capital investment in buildings and furnaces. The unloading of such furnaces is quite dim cult and tedious because of the adjacent hot furnaces and because of the necessity of using large amounts of hand labor to remove the silicon carbide from the furnace due to the proximity of the adjacent furnaces and the difficulty of using mechanical unloading equipment in the restricted floor space available. This also requires that the furnaces be cooled in extraordinary long time before unloading in order to get the temperature down to the point where the hand labor can be effectively used. A further problem arises in the loading of such furnaces because of the adjacent other furnaces. This means lengthy conveyor belts'from the mixing bins to the furnaces or overhead cranes carrying successive bucket loads to the furnace.

We have invented a silicon carbide furnace and plant which eliminates these problems and makes it possible to produce a given quantity of silicon carbide in a plant area less than /3 the size of that required by conventional methods.

Preferably we provide an electrical power source. a main trackway adjacent said power source, a furnace bottom mounted on wheels on said trackway movable to and away from said power source, said furnace bottom having a substantially fiat heat resistant surface, removable sides along each side of said surface and removable ends on: said surface, said sides and ends defining a heating chamber, electrode means in each of said ends, removable connections between said electrode ends and said power source, a transfer car movable transversely to the main trackway and having a corresponding trackway adapted to be alignedw'ith the main trackway to receive the furnace bottom whis ls and furnace whereby said furnace may be moved transversely to said main trackway, a service area spaced from said main trackway by said transfer car, secondary trackways in said service area receiving said furnace from said transfer car, loading means at said service area adapted to load said furnace and a cooling and unloading section in said service area spaced from the loading means. Preferably the loading means is a gravity discharge hopper or the like located over. a trackway adapted to receive a furnace to be loaded from the transfer car. Other loading device and conveying equipment, may of course, be used. The removable ends of said furnace are preferably provided with cooling means removably connected to a source of coolant adjacent the power source whereby the electrodes in the ends can be cooled.

In a preferred embodiment, the sides are a plurality of side-by-side cast iron panels lined with refractory and removed and replaced by crane, loader or similar j lifting device. a

In the foregoing general description of our invention we have set out certain objects, purposes and advantages i of our invention. Other objects, purposes and advantages will be apparent. from a consideration of the following description and the accompanying drawings in which:

FIGURE 1 is a plan view of a silicon carbide plant floor according to our invention;

FIGURE 2 is a side elevation of a silicon carbide furnace according to our invention;

FIGURE 3' is a top plan view of the furnace of FIG- URE 2;

FIGURE 4 is a section on the line IV-IV of FIG- UREZ;

FIGURE 5 is a section on the line VV of FIG- URE 2; and 1 FIGURE 6 is an enlarged fragment elevation of the furnace end and clamping device.

Referring to the drawings we have illustrated in FIG- URE l a furnace building floor 10 having three transformer units 11, 12, and 13. Ajacent each transformer unit is a pair of trackways l4a-l4b, a-15b, and 16a- 1 16b each made up of spaced rails. A transfer pit 17 is provided at the end of the trackways remote from transformer unitsand extending transverse to the length of the trackways. Rails 18, 19, 20 and 21 are provided in the pit to carry a transfer car 22 mounted on wheels 23 riding on rails l8, 19, 20 and 21. A trackway 24 is mounted on the transfer car 22 level with the plane" of trackways l4a-l4b, l5a-l5b, and l6a-16b and adapted tobe selectively aligned with any one of said trackw'ays by movement of the transfer car. The transfer car is driven by any of various well-known drive means from end to end of pit 17 to a align tracltway 24 with the furnace floor trackways. A service area 25 is provided adjacent pit 17 on the side opposite furnace floor 10. The service area is provided with a stripping floor 26 having a trackway 27 on the same plane as track'ways l4a-l4b, 15a-15b, and 1641-161). A loading floor 28.

is also provided in service area 25 and it too is provided with a trackway 29 on the same plane as trackways 14a-14b, 15a-15b, and l6al6b Both trackways 27 and 29 terminate at pit 17 so that trackway 24 on transfer car 22 may be aligned with them. An overhead loading hopper (not shown) is provided adjacent trackway 29 to discharge by gravity over trackway 29.

A furnace car 10 having a furnace bottom 30 mounted on wheels 31 is adapted to move on wheels 31on the several trackways 14al4b, lSu-lSb, l6a-16b, 24, 27 and 29. A heat resistant surface, 32 is provided on the bottom 30. This surface may beof cast concrete, brick or any of various well-known refractory materials. Identical end panels 33 are removably mounted on each end of the bottom 30. These end panels are made up of a steel frame 34 carrying a cast concrete end member 35 having a refractory face 36 of high temperature brick or Patented Mar. 11, 1969 like refractory material and provided with an opening 37 receiving an electrode 38.

A plurality of removable side panels 40 extend along each side of the bottom between the two end panels 33 to form a trough likereceptacle. The side panels 40 are made up of an inclined bottom plate 41 and vertical side plate 42 of cast iron or like material carried by a supporting frame 43. The bottom plate 41 and side plate 42 are lined with refractory brick 44..The two bottom plates 41 from opposite sides meet generally at the center line of bottom surface 32 to form a generally U-shaped bottom on the receptacle. The electrodes 38 are connected to transformers 11, 12 or 13 by means of cables 50 and busbars 50a, each busbar serving a pair of furnaces, and removable electrode clamps 51. The clamps 51 are preferably water cooled by water introduced into passages in the clamps by water lines 52.

The operation of the plant and furnace of our invention is as follows. The end panels 33 with electrodes 38 mounted in openings 37 are placed on bottom surface 32. The side panels 40 are then placed on bottom surface 32 to complete the furnace. The end panels and side panels may be placed in position by a high-lift, overhead crane, traveling floor crane or like device. This work is done on the trackway 27 on the stripping floor. The furnace car is then moved from trackway 27 onto trackway 24 on transfer car 22 by means of a high-lift, a winch and cable or any of well known means. The transfer car 22 is then moved to trackway 29 where the furnace car is moved onto trackway 29 and loaded by gravity. The furnace charge is a conventional charge for the Acheson process, i.e., silica and carbon around a carbon electrode core. In the meantime a furnace car ready for stripping may be moved into the stripping area asdescribed hereafter. The furnace car is loaded from the hopper previously described or by some other conventional means and is then returned to the transfer car which is moved to one of trackways 1411-14b, lSu-lSh, or 1611-161). The loaded car is moved onto one of the furnace floor trackways to a position adjacent one of the transformers 11, 12 and 13. Clamps 51 are applied to electrodes 38 which are in contact with carbon electrode cores 60 of the furnace charge. The electrical current is applied from the transformer along with water coolant for the clamp. When the charge has been heated to the required temperature and time for conventional Acheson process silicon carbide, the electrical current is stopped and the clamps are removed from electrodes 38. The clamps are then moved to a furnace car on the next adjacent track of a pair of example 14a-14b. This adjacent car is then heated while the just completed car cools. Prior to completion of the heating process on the second adjacent car, the first car is removed from the furnace floor trackway onto transfer car 22 and from there to trackway 27 on the stripping floor and a newly loaded car positioned in its place ready to receive the clamps 51 on completion of the second car.

' When the furnace car is moved onto trackway 27, the side panels 40 are lifted off the bottom surface and the contents of the car pushed off bottom surface 32 onto the stripping floor 26 by means of a high-lift or like device and moved to a storage or loading area. The side panels 40 are replaced and the car is ready to repeat the cycle.

The advantage in time saved and labor saved as well as capital investment in buildings and fixed furnaces by our invention will be obvious to persons familiar with conventional silicon carbide plants. Hand labor is substantially eliminated in the plant of our invention whereas it makes up a very large part of the conventional practices. Much time is saved because unloading can be-done at much higher temperatures by the simple expedient of pushing the completed charge off the fiat bottom car surface rather than digging it piece by piece from the fixed furnaces of the prior art and loading'it in the restricted areas between such furnaces.

While we have illustrated and described certain preferred embodiments and practices of our invention it will be understood that this invention may be otherwise embodied within the scope of the following claims.

We claim:

1. A silicon carbide manufacturing plant comprising an electrical power source, a main trackway adjacent said power source, a furnace car movable on said trackway to and from said power source, a refractory bottom on said car, removable side and end panels on said refractory bottom of said furnace car, said side and end panels being interconnected to form a heating chamber on said car, electrode means in each end pane], removable connections between said power source and electrode means, a transfer car movable on a trackway extending transversely to the main trackway, said transfer car carrying a trackway corresponding to said main trackway and alignable with the main trackway receiving the furnace car therefrom, a service area opposite the main trackway and spaced from said main trackway by said transfer car, a secondary trackway on said service area receiving said furnace car from said transfer car trackway, loading means in the service area for loading said heating chamber while on said secondary trackway and an unloading section in said service area spaced from the loading means and receiving a completed furnace charge from said furnace car.

2. A silicon carbide manufacturing plant as claimed in claim 1 wherein cooling means are provided on each electrode.

3. A silicon carbide manufacturing plant as claimed in claim 1 wherein the loading means includes an overhead receptacle above a portion of said secondary trackway.

4. A silicon carbide manufacturing plant as claimed in claim 1 wherein a pair of trackways are provided adjacent each power source, each trackway receiving a furnace car.

5. A silicon carbide manufacturing plant as claimed in claim 1' wherein said transfer car is movable on tracks in a pit transverse to the main trackway.

6. A silicon carbide manufacturing plant as claimed in claim 1 wherein the side panels include an inclined lower portion terminating adjacent the center line of the car.

7. A silicon carbide manufacturing plant as claimedv in claim 1 having clamp means removable engaging said electrode means in each end panel, connections between said clamp means and said source of electrical power, cooling means on said. clamp means, a source of coolant, and connections from said source of coolant to said coolingmeans.

8. A silicon carbide manufacturing plant as claimed in claim 7 wherein the cooling means are coolant passages within the clamp means.

9. In a silicon carbide manufacturing plant having an electrical power source, and a main trackway adjacent said power source, the improvement comprising a furnace car adapted to move on said trackway to and from said power source, a refractory bottom on said car, removable side and end panels on said refractory bottom of said furnace car, said side and end panels being interconnected to form a heating chamber on said car, electrode means in each end panel, removable connections between said power source and electrode means, a transverse trackway intersecting said main trackway at a level below the main trackway and carrying a movable transfer car having a trackway alignable with the main trackway, a service area spaced from said main trackway by a transfer car, a secondary trackway in said service area receiving said furnace car from said transfer car, loading means in the service area adapted to load said heating chamber while on said secondary trackway and an unloading section in said service area spaced from the loading means and receiving a completed furnace charge from said furnace car.

10. In a silicon carbide manufacturing plant as claimed 3,155,758 11/1964 Hill 13-25 in claim 9 wherein the electrode connections are pro- 3,305,619 2/ 1967 Molstedt et a1. vided with cooling means. OTHER REFERENCES References Cited The Manufacture of Iron & Steel, vol; 3, Chapman & UNITED STATES PATENTS 5 Hall, Ltd., London, 1960, TN 705 B25 1957, pp. 83, 84. 1

2,122,469 7/1938 Hitner 13-6 Moore A. P ary Exammflh 2,263,549 11/ 1941 Peyches 13-6 X H. B. GILSON, Assistant Examiner. 2,629,756 2/1953 Wilkins et a1. 13-33 X 10 2,694,097 11/1954 Collin 13-34 X U.S.CI.X.R.

2,899,476 8/1959 Gel] 13-6 13--3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,432,605 March 11, 1969 Wilbur T. Bolkcom et al.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 49, cancel "a"; line 57, "16b" should read 16b. line 62, "10" should read 100 Signed and sealed this 31st day of March 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, J r.

Commissioner of Patents Attesting Officer 

